"When?" is the Most Important Question for Entrepreneurs. (The Answer: Now?)When do you launch? When do you act? When do you change? The cofounder of Square has answers.

I am an entrepreneur, but I am also a glassblower, and every glassblower has amentor.

In fact, we all have the same one:Lino Tagliapietra. Glassblowing is the only profession I know where everyone agrees on who the best practitioner is. Nobody knows who the bestaccountantor mortician or loan shark is, but the world's best glassblower is Lino.